Surface Of Palladium Nanoparticles Research Articles

Biogenic and rapid route for the synthesis of palladium nanoparticles by using Roylea cinerea extract and their catalytic activity for Suzuki and Sonogashira coupling reactions and nitrophenol reduction

4-nitrophenol is a serious environmental pollutant due to its carcinogenic, mutagenic, and teratogenic properties, posing serious risks to aquatic life, plants, and humans even at very low concentrations. In the current work a simple, inexpensive, and ecologically appropriate approach for generating palladium nanoparticles (Pd-NPs) from palladium chloride and their potential for the reduction of 4-nitrophenol have been investigated. This method employs a non-toxic aqueous extract obtained from the aerial portion of Roylea cinerea, which functions as both a reducing and stabilizing agent. The Pd-NPs synthesis was confirmed through UV–vis spectroscopy, and were further characterized by techniques like FT-IR, SEM, EDX, and XRD analysis. The biosynthesized Pd-NPs had a spherical shape with diameters ranging from 20 to 30 nm. The presence of palladium in the Pd-NPs was confirmed by EDX analysis. The available functional groups on the surface of Pd-NPs were determined through FTIR analysis. Pd-NPs demonstrated catalytic efficacy in both Sonogashira and Suzuki coupling processes, as measured by UV–vis spectrophotometry during nitrophenol reduction. The findings demonstrate that the Pd-NPs exhibited significant catalytic efficiency, achieving the degradation of over 95 % of 4-nitrophenol within a 16-min timeframe. Following the catalytic reaction, the catalyst was effortlessly recovered through centrifugation, demonstrating its ability to undergo multiple catalytic cycles without a significant loss of activity (>90 % after five cycles).

Phosphate-supported palladium single atom and nanoparticle boost ambient temperature tandem hydrogenolysis–hydrogenation of furan alcohols/aldehydes

Developing a one-pot method for tandem hydrogenolysis–hydrogenation of biomass-derived furan-based alcohols to methyltetrahydrofurans is challenging but crucial for synthesizing sustainable biofuels and chemicals. Herein, we report the efficient hydrogenolysis–hydrogenation of furan alcohol to 2-methyltetrahydrofuran using a phosphate-supported synergistic palladium single atom and nanoparticle at an ambient temperature. Comprehensive characterizations and theoretical calculations reveal that in situ H2 heterolysis at the palladium single atom–AlPO4 interface generates frustrated Lewis H+–H− pairs, which selectively cleaves the C–OH bond in furan alcohol to form 2-methylfuran, and H atoms on the palladium nanoparticle surface promotes the subsequent CC hydrogenation of 2-methylfuran to 2-methyltetrahydrofuran. Additionally, the catalyst shows generality for various furan and heterocyclic alcohols. Furthermore, the catalyst exhibits excellent activity in the hydrogenation–hydrogenolysis–hydrogenation of furan aldehydes to methyltetrahydrofurans. The results provide a highly efficient reaction for synthesizing methyltetrahydrofurans at ambient temperature, which has excellent potential for industrial applications.

Carbon Monoxide Oxidation on the Surface of Palladium Nanoparticles Optimized by Reinforcement Learning

Carbon Monoxide Oxidation on the Surface of Palladium Nanoparticles Optimized by Reinforcement Learning

Green Synthesis, Functionalization and catalytic Activity of Palladium nanoparticles for development of Eco-friendly methods

During the past few decades metal nanoparticles are in the forefront of research for their unique properties and wide range of versatile applications. Among the several transitional metal nanoparticles palladium nanoparticles (PdNPs) are most interesting for their superior catalytic activity towards several organic reactions and also used as recyclable catalyst. Now being the time when environmental issue is a great concern and needs development of environmentally benign process. Synthesis of PdNPs using non-toxic chemicals and solvents, mild reaction condition, bio-degradable reducing or stabilizing agent, alternative energy sources are energy efficient and also cost effective and considered as green process Functionalization on the surface of PdNPs, nanoparticles showed excellent catalytic activity and can perform organic reactions in eco-friendly conditions. In this review different green synthetic methods, surface functionalization and catalytic activity of PdNPs towards several C-C coupling reactions, toxic dye degradations are discussed.

Palladium-graphene hybrid as an electrocatalyst for hydrogen peroxide reduction

The electrocatalytic reduction of hydrogen peroxide in an alkaline solution has been studied on a hybrid material based on hydrothermally obtained palladium particles supported on graphene (Pd@G). The morphology, structure, and chemical composition of the prepared hybrid material, including spatial distribution of palladium nanoparticles, were examined by SEM, XRD, EDX, elemental mapping, XPS, FTIR, and BET. The hydrogen peroxide reduction reaction (HPRR) was studied by cyclic and square wave voltammetry in an oxygen-free and air-saturated alkaline medium. The Pd@G exhibited pronounced electrocatalytic activity for HPRR, which proceeds via complex electrode mechanisms coupled with adsorption phenomena and hydrogen peroxide disproportionation reaction as a heterogeneous chemical process on the surface of palladium nanoparticles.

A continuous electroreduction cell composed of palladium nanocatalyst immobilized on discarded cigarette filters as an active bed for Cr(VI) removal from groundwater

In this research, a unique continuous electrochemical cell was designed and applied for the disinfection of groundwater and simultaneous Cr(VI) reduction and Cr(III) precipitation. Discarded cigarette filters (DCFs) were utilized as an efficient bed for palladium nanoparticles (PdNPs) immobilization located between porous anode and cathode made of graphite felt. The characterization of the bed was performed using FE-SEM, EDS, BET, and FT-IR analysis. The results confirmed the distribution of palladium nanoparticles on the surface of DCFs. The proposed design for electrochemical cell obviated the need to divide the anolyte and catholyte because the anode was located at the outlet of the cell, thereby avoiding the reaction between hydrogen radicals produced on the surface of PdNPs and oxygen and chlorine produced in the anode. The hydrogen gas produced in the cathode was converted to hydrogen radicals, acting as the most prominent species for the reduction. Hydroxide ions produced in the cathode increased the pH of the solution between electrodes, resulting in the precipitation of Cr (III) with an efficiency of 96%. Furthermore, free chlorine at the concentration of 1 mg L−1 was generated through chloride ion oxidation in the anode, which can be effective for disinfection. The effect of initial Cr (VI) concentration (C0), flow rate (Q), and current (I) was investigated, and the maximum removal efficiency (99.7%) was observed at the flow rate of 5 mL min−1 and current of 0.05 A, respectively. No interference ensued from the various coexisting ions in groundwater. The findings of this study suggested that the proposed electrochemical cell is capable of in-situ total chromium removal and free chlorine production in groundwater simultaneously.

Synthesis and Characteristics of Ag–Pd Nanoparticles: Inhibition of Palladium Surface Catalytic Activity by Silver

Palladium nanoparticles catalyze the reduction of Ag+ ions with hydrogen on their surface, thereby leading to the formation of bimetallic particles with the “core–shell” structure. The catalytic reaction of methylviologen reduction with hydrogen at ratio [Ag] : [Pd] > 1 is suppressed by silver atoms located on the surface of palladium nanoparticles. At [Ag] : [Pd] ≤ 1, the reduction takes place; however, it is preceded by an induction period, and, the higher the silver content on the nanoparticle surface, the longer the induction period. The rate constant of the catalytic reduction, which begins after the end of the induction period, decreases with increasing silver content on the surface of palladium nanoparticles.

A New Redox Technique for Depositing CrOx on the Surface of Pd(0) Nanoparticles: Catalysts for Selective Phenylacetylene Hydrogenation

A catalyst containing chromium oxide particles on the surface of palladium nanoparticles is synthesized for the first time using a redox technique for reduction with adsorbed hydrogen. The low-temperature reduction of chromium oxide and formation of palladium hydride is reported for the first time in such catalyst. A considerable difference between its catalytic properties in the selective hydrogenation of phenylacetylene and those of the initial palladium catalyst is shown.

A highly-sensitive electrocatalytic measurement of nitrate ions in soil and different fruit vegetables at the surface of palladium nanoparticles modified DVD using the open bipolar system

In the present research, a nanoparticle-modified recordable digital versatile disc (DVD) blade was used as a bipolar electrode to design a bipolar electrochemical method for nitrate ion measurement. The DVD blade was modified with copper and palladium nanoparticles. In the proposed setup, using a direct power supply and an appropriate potential, the electrocatalytic reduction of nitrate ions occurred at the cathode, and, simultaneously, the oxidation reaction of a silver layer was performed at the anode of the bipolar electrode. The oxidation process led to the dissolution of the silver layer. The results indicated that the length of the layer dissolution on the anode surface at a given time was directly related to the concentration of the nitrate ions in the analytical solution. Based on the proposed method, the electrochemical measurement of nitrate ions took place in two linear ranges between 0.5 and 3500.0 μM and a detection limit of 0.16 μM. Finally, this method was used to determine nitrate ion concentration in a mineral water, agricultural soil, cucumber, tomato, and bell pepper.

A New Redox Method for Depositing FeOx on the Surface of Pd(0)/SiO2 Nanoparticles—Catalysts for Selective Phenylacetylene Hydrogenation

A catalyst containing iron oxide particles on the surface of palladium nanoparticles is synthesized for the first time using a redox method of the catalytic reduction with hydrogen. The activity of the catalyst in the selective hydrogenation of phenylacetylene considerably increased, compared to the initial palladium catalyst.

Identification of Active Sites in Oxidation Reaction from Real-Time Probing of Adsorbate Motion over Pd Nanoparticles.

Obtaining insight into the type of surface sites involved in a reaction is essential to understand catalytic mechanisms at the atomic level and a key for understanding selectivity in surface-catalyzed reactions. Here we use ultrafast broad-band vibrational spectroscopy to follow in real-time diffusion of CO molecules over a palladium nanoparticle surface toward an active site. Site-to-site hopping is triggered by laser excitation of electrons and followed in real-time from subpicosecond changes in the vibrational spectra. CO photoexcitation occurs in 400 fs and hopping from NP facets to edges follows within ∼1 ps. Kinetic modeling allows to quantify the contribution of different facet sites to the catalytic reaction. These results provide useful insights for understanding the mechanism of chemical reactions catalyzed by metal NPs.

Palladium Carbide and Hydride Formation in the Bulk and at the Surface of Palladium Nanoparticles

The presence of a core/shell behavior in Pd nanoparticles (NPs) during the formation of the metal-hydride phase has recently been highlighted combining X-ray absorption and scattering experiments [J. Phys. Chem. C 2017, 121, 18202]. In this work, we focus on the formation of the carbide phase in the bulk region and on the surface of supported palladium NPs because it affects the catalytic activity and selectivity in hydrogenation reactions. We present in situ X-ray absorption spectroscopy study of carbide formation and decomposition in 2.6 nm palladium nanoparticles supported on carbon during exposure to acetylene, hydrogen, and their mixtures at 100 °C, taken as a representative temperature for hydrogenation reactions. Fourier analysis of extended X-ray absorption fine structure (EXAFS) spectra was used to determine the average Pd–Pd bond distance in the NPs, reflecting the formation of bulk palladium carbide, while theoretical calculation of X-ray absorption near-edge structure (XANES) using the finite ...

Halide-Enhanced Catalytic Activity of Palladium Nanoparticles Comes at the Expense of Catalyst Recovery

In this communication, we present studies of the oxidative homocoupling of arylboronic acids catalyzed by immobilised palladium nanoparticles in aqueous solution. This reaction is of significant interest because it shares a key transmetallation step with the well-known Suzuki-Miyaura cross-coupling reaction. Additives can have significant effects on catalysis, both in terms of reaction mechanism and recovery of catalytic species, and our aim was to study the effect of added halides on catalytic efficiency and catalyst recovery. Using kinetic studies, we have shown that added halides (added as NaCl and NaBr) can increase the catalytic activity of the palladium nanoparticles more than 10-fold, allowing reactions to be completed in less than half a day at 30 °C. However, this increased activity comes at the expense of catalyst recovery. The results are in agreement with a reaction mechanism in which, under conditions involving high concentrations of chloride or bromide, palladium leaching plays an important role. Considering the evidence for analogous reactions occurring on the surface of palladium nanoparticles under different reaction conditions, we conclude that additives can exert a significant effect on the mechanism of reactions catalyzed by nanoparticles, including switching from a surface reaction to a solution reaction. The possibility of this switch in mechanism may also be the cause for the disagreement on this topic in the literature.

Biofabrication of polyphenols coated Nano palladium and its in-vitro cytotoxicity against human leukemia cell lines (K562)

The biofabrication of palladium nanoparticles (PdNPs) using aqueous leaf extract of Pelargonium graveolens is reported herein. The polyphenols present in the Pelargonium graveolens extract are mainly responsible for reduction and subsequent stabilization of formed PdNPs. UV–Visible spectroscopy (UV–Vis) absorption and reaction color change from yellow to brown indicated the formation of PdNPs. The as synthesized PdNPs were studied by using characterization techniques such as Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), Energy dispersive spectroscopy (EDS), Zeta potential measurements and Selected area electron diffraction (SAED). FTIR analysis and Zeta potential measurements showed the capping of polyphenols onto the surface of PdNPs, which further responsible for preventing aggregation of PdNPs. TEM image showed that the PdNPs exists in the range from 50 to 150nm. Also, XRD pattern revealed the crystalline nature of as synthesized PdNPs. The in vitro cytotoxicity studies of Pelargonium graveolens extract capped PdNPs was conducted using human leukemia cell lines (K562) by following an MTT cell viability assay and is found that the cytotoxicity is dose dependent. Further, the synthesized PdNPs will open a new opportunities in the field of biomedicine. Also, the produced method is an alternative to the chemical synthetic approaches that are being used nowadays.

Reactivity of CO on Sulfur-Passivated Graphene-Supported Palladium Nanocluster Arrays

Nanocluster arrays on graphene are suitable model systems for catalysis. We use this model system to study sulfur poisoning, which is a major deactivation process of heterogeneous catalysts. Using high-resolution X-ray photoelectron spectroscopy, we investigated the adsorption and desorption of CO on sulfur-poisoned graphene-supported palladium nanoparticles. We find that sulfur blocks CO adsorption sites, with hollow sites being most affected. From the unchanged desorption temperatures, we conclude that the Pd–CO bond strength is not altered by co-adsorbed sulfur. The degree of site blocking compared to the amount of sulfur indicates that the palladium nanoparticle surface is dominated by (111) and (100) facets.

The adsorbed state of a thiol on palladium nanoparticles.

In the present work, a combination of imaging, spectroscopic and computational methods shows that 1-dodecanethiol undergoes S-deprotonation to form 1-dodecanethiolate on the surface of palladium nanoparticles, which then self-assembles into a structure that shows a high degree of order. The alkyl chain is largely in the all-trans conformation, which occurs despite the small size of the nanoparticle, (mean diameter = 3.9 nm). Inelastic neutron scattering spectroscopy is readily able to characterise organic surface layers on nanoparticles; the nature of the material is irrelevant: whether the nanoparticle core is an oxide, a metal or a semiconductor makes no difference. Comparison to DFT calculations allows insights into the nature and conformation of the adsorbed layer.

ChemInform Abstract: Catalytic Properties of Unsupported Palladium Nanoparticle Surfaces Capped with Small Organic Ligands

AbstractReview: 105 refs.

Catalytic Properties of Unsupported Palladium Nanoparticle Surfaces Capped with Small Organic Ligands.

This Minireview summarizes a variety of intriguing catalytic studies accomplished by employing unsupported, either solubilized or freely mobilized, and small organic ligand-capped palladium nanoparticles as catalysts. Small organic ligands are gaining more attention as nanoparticle stabilizers and alternates to larger organic supports, such as polymers and dendrimers, owing to their tremendous potential for a well-defined system with spatial control in surrounding environments of reactive surfaces. The nanoparticle catalysts are grouped depending on the type of surface stabilizers with reactive head groups, which include thiolate, phosphine, amine, and alkyl azide. Applications for the reactions such as hydrogenation, alkene isomerization, oxidation, and carbon-carbon cross coupling reactions are extensively discussed. The systems defined as "ligandless" Pd nanoparticle catalysts and solvent (e.g. ionic liquid)-stabilized Pd nanoparticle catalysts are not discussed in this review.

Palladium nanoparticle's surface structure and morphology effect on the catalytic activity for dry reforming of methane

Low loaded Pd/α-Al2O3 catalysts (<0.5wt% Pd) were characterized and tested for CH4 reforming with CO2 at 650°C. The catalysts were prepared by a recharging procedure, using an organometallic precursor, followed by intermediate washing and calcination steps. FTIR spectra of adsorbed CO showed that the Pd surface structure and the particle size were dependent on the number of post-impregnation washing steps. A catalyst sample with a metal dispersion of 33% showing well defined low-index planes (by FTIR) and nearly spherical particles (by TEM) was obtained using two-washing steps. In the reaction, it exhibited a high initial activity followed by a pronounced deactivation due to carbon nanofiber's formation and sintering. TEM analysis of the used catalyst revealed the presence of spherical Pd particles at the end of the fibers that were not attached to the support surface. On the other hand, a high dispersion sample (78%) with a large fraction of Pd atoms with low coordination was obtained by applying three washing steps after impregnation. The presence of small hemispherical particles and larger nearly-flat ones attached to the support were found by TEM. In this case, the catalyst initially showed a very low activity that increased slowly up to a steady value. Although sintering also occurred and the surface structure of the used catalyst resembled the one of the low dispersion catalyst, the amount of carbon formed was quite low. The observed activation under reaction conditions was associated with the slow development of a surface structure that exhibited mainly the (100) plane favoring methane dissociation. However, the initial interaction of the particles with the support suggested by TEM micrographs seems to remain unaltered despite the particle size increase. Consequently, the process of nanofiber formation and particle separation was inhibited.

Electrocrystallization of palladium (Pd) nanoparticles on platinum (Pt) electrode and its application for electro-oxidation of formic acid and methanol

Palladium nanoparticles (PdNPs) were synthesized on Platinum (Pt) electrode by employing a potentiostatic pulse method of electrodeposition. The mechanism of electrocrystallization of PdNPs on Pt was investigated in the system containing 1mMK2PdCl4 in 0.1M H2SO4. Experimental results show that Pd electrodeposition follows the so-called Volmer–Weber growth mechanism. The electrodeposited PdNPs were characterized by X-ray photoelectron spectroscopy (XPS) and Field emmisision scanning electron microscopy (FESEM). The results obtained suggested the presence of chemisorbed oxygen on the surface of PdNPs. The influence of time of deposition on the size and monodispersity of the deposited PdNPs was investigated. The studies revealed that, the size of PdNPs increased with increase in the time of deposition. The synthesized Pd nanoparticles modified Pt electrode displayed significantly different voltammetric behavior compared to bare Pt electrode and also showed high catalytic activity towards the electrooxidation of formic acid and methanol. To the best of our knowledge, this is the first report of electrosynthesis of Pd nanoparticles using potentiostatic pulse method without using any stabilizing agent or template.